Book Image

Learning Apache Cassandra - Second Edition

Book Image

Learning Apache Cassandra - Second Edition

Overview of this book

Cassandra is a distributed database that stands out thanks to its robust feature set and intuitive interface, while providing high availability and scalability of a distributed data store. This book will introduce you to the rich feature set offered by Cassandra, and empower you to create and manage a highly scalable, performant and fault-tolerant database layer. The book starts by explaining the new features implemented in Cassandra 3.x and get you set up with Cassandra. Then you’ll walk through data modeling in Cassandra and the rich feature set available to design a flexible schema. Next you’ll learn to create tables with composite partition keys, collections and user-defined types and get to know different methods to avoid denormalization of data. You will then proceed to create user-defined functions and aggregates in Cassandra. Then, you will set up a multi node cluster and see how the dynamics of Cassandra change with it. Finally, you will implement some application-level optimizations using a Java client. By the end of this book, you'll be fully equipped to build powerful, scalable Cassandra database layers for your applications.
Table of Contents (14 chapters)

Collection columns and concurrent updates


Thankfully, Cassandra's collection columns allow us to bypass the entire read-mutate-write process, allowing us to express the exact operation we want to do in CQL without regard to the current value of the column.

Defining collection columns

Given the limitations of the serialized approach, let's drop our text column and replace it with a collection column of the same name. Cassandra offers three flavors of collections: lists, sets, and maps. We'll explore all three in this chapter, starting with a set column, which is the most appropriate for our starred_by_users column:

ALTER TABLE "user_status_updates" 
DROP "starred_by_users"; 

ALTER TABLE "user_status_updates" 
ADD "starred_by_users" SET<text>; 

The last line introduces a new syntax to define a collection column type. The new column that we have created is a collection column using the SET data structure; the values it contains have type text. Like normal scalar data columns, collection...